1. Field of the Invention
The invention relates to an axisymmetric, converging-diverging, turbojet-engine exhaust nozzle.
2. Description of the Related Art
More specifically, the invention relates to an axisymmetric, converging-diverging, turbojet-engine exhaust nozzle comprising a ring of converging flaps which hinge on the downstream end of a stationary, annular structure and a ring of diverging flaps which hinge on the downstream end of the converging flaps. Moreover, the diverging flaps connect to a vectoring ring driven by a plurality of linear actuators mounted on the stationary structure in order to regulate the exhaust cross-section and deflect the exhausted gas flow relative to the turbojet-engine axis.
Axisymmetric, converging-diverging exhaust nozzles direct exhaust gas aftward from the aircraft in order to achieve vectored thrust and increased manoeuverability in combat aircraft. Movement of these nozzles is achieved by diverging flaps that are linked to the vectoring ring by secondary cold flaps or by linkrods hinging on the downstream ends of the diverging flaps. When longitudinal displacements of actuator rods are implemented in mutually different ways, the plane of the vectoring ring tips relative to the turbojet-engine axis, and as a result, the secondary cold flaps or the linkrods connected to the ends of the diverging flaps are driven. Consequently, the flow path subtended by the plurality of the diverging flaps slants relative to the turbojet-engine axis. Additionally, when the actuator rod displacements are identical, the vectoring ring translates, making it possible to change the exhaust cross-section of the nozzle""s diverging portion.
Maintenance of a well controlled slant angle requires the vectoring ring to be kept in a position relative to the stationary annular structure. Moreover, the slope of the thrust vector entails a differential pressure distribution on the periphery of the diverging flaps or on the secondary cold flaps or linkrods connecting the vectoring ring to the diverging flaps. As a result, lateral loads are applied to the vectoring ring connected to the nozzle""s stationary structure.
Several designs are known to keep the vectoring ring substantially concentric with the turbojet-engine axis and to prevent it from moving sideways on account of the above cited lateral loads.
In the patent document WO 92/03649, the vectoring ring comprises three radial stubs directed outward and equidistant by 120xc2x0 around the axis and sliding in axial apertures between pairs of parallel rails which are solidly joined to the stationary structure and of which the center planes intersect along the turbojet-engine axis. In this design, the center of the vectoring ring defined by the intersection of the stub axes is ideally situated on the turbojet-engine axis. However, the pressure-generated radial torques in the link between the stubs may entail deleterious friction for the jet-deviation position.
In U.S. Pat. No. 5,239,815, the vectoring ring is positioned by a spherical wall solidly affixed to this vectoring ring resting against an outside wall firmly joined to the stationary structure. The lateral loads are absorbed by rollers supported on the ring that roll inside rails connected to the stationary structure.
In U.S. Pat. No. 5,174,502, the vectoring ring is driven into position and the lateral loads are absorbed by rectangular slides solidly joined to the stationary structure while being independent of the linear actuators. The slides are connected, to the vectoring ring by swivels integrated into joints radially hinging on the slide.
The object of the invention is to integrate the control and positioning of the vectoring ring by linear actuators which absorb the lateral loads caused by the vectored jet of exhaust gases.
The invention achieves its objective in that the proposed exhaust nozzle is characterized by the linear actuators connected in a swiveling manner to the vectoring ring and mounted on the stationary structure in such a way to position the vectoring ring and to absorb the tangential loads applied by the exhaust gases on the diverging flaps.
In a first embodiment of the invention, the linear actuator comprises a case hinging upstream on the stationary structure to allow pivoting motion in a radial plane, a sheath connected by the swivel to the vectoring ring and capable of sliding over the outside surface of the actuator case, and a piston mounted in a sliding manner inside the actuator case wherein the piston rod is firmly joined to the sheath.
Preferably the end of the piston rod connects to the sheath""s end wall by a sliding connection element.
Advantageously the sheath slides between two rollers connected to the stationary structure.
In a second embodiment of the invention, the linear actuator comprises a case hinging upstream on the stationary structure in order to pivot in a radial plane, a piston sliding in said case and a piston rod in which one end is connected by a swivel to the vectoring ring.
Advantageously the actuator case slides radially between two guides firmly affixed to the stationary structure.
In a third embodiment of the invention, the linear actuator comprises a case affixed to the stationary structure, a piston sliding in the actuator case and a piston rod in which an end is connected in a swiveling manner to a linkrod which in turn radially hinges on the vectoring ring.
In an embodiment variation of the invention, the vectoring ring consists of two parts which hinge on two diametrically opposite hinges